There has been nothing subtle about the ad wars between Tammy Baldwin and Tommy Thompson. The anti-Baldwin ads scream “Liberal!” The anti-Thompson ads scream, “Lobbyists!”

That’s our US Senate race in a nutshell, or at least the TV version.

Here’s a look at how the Thompson-Baldwin race has played out on television, based on data gathered by Kantar Media CMAG, a D.C. firm that tracks political ads:

Tone. In the 30 days that ended on Oct. 2, 92% of the ads aired in this contest were “negative,” which means they contained attacks on the opposing candidate. That’s in keeping with what has been the most negative presidential election in recent memory, according to a recent study by the Wesleyan Media Project. In the first three weeks after the party conventions, only 8% of presidential ads were “positive,” compared to 29% for the same period in 2008.

Volume. Millions have been spent pillorying both Baldwin and Thompson. But the key shift so far in the this race -- when Thompson lost the longtime lead he had in head-to-head matchups against Baldwin – occurred in the weeks following the Aug. 14 GOP Senate Primary, when there was a big Democratic edge on television. Thompson’s campaign was broke after he won a tough primary and he was temporarily outgunned. Between Aug. 19 and Sept. 17, Baldwin and her allies outspent Thompson and his allies almost 3-to-1 on broadcast television, according to CMAG. (The charts below capture only part of the advertising picture; they reflect estimates of broadcast ads, but not cable or radio or ad time for spots not yet aired):

In recent weeks, things have largely evened out, according to CMAG estimates:

But the shift in the race had already occurred. In surveys by both Marquette Law School and Public Policy Polling, Thompson went from leading Baldwin in mid-August to trailing her in September:

Come Nov. 6, we’ll know whether that was a turning point in this very competitive race, or just a bump in the road for Thompson.

"It’s not magic. When both sides are at equal levels, ads are not likely to move the race very much. But when attitudes are less formed and one side has a big advantage, you’re more likely to see ad effects,” says Ken Goldstein, the political scientist who runs CMAG. “We keep forgetting Tommy Thompson hasn’t been on the ballot in what, 14 years? To have such an onslaught introducing a different-sounding or different-looking Tommy Thompson has the potential to be quite effective.”

Independent spending. Outside groups have played a huge role in the ad wars. When Wesleyan looked at all Senate races during the last three weeks of September, independent groups accounted for a larger share of the ad spending in Wisconsin than in all but two other Senate races, Ohio and Virginia.

They have been especially important on the Republican side this fall because of Thompson’s money struggles. Between Sept. 3 and Oct. 2, the Thompson campaign accounted for only one quarter of the broadcast TV spending on the GOP side. Outside groups made up the rest, led by Crossroads GPS and the US Chamber of Commerce. By contrast, Baldwin in this period accounted for almost half the total Democratic spending on broadcast TV. An array of groups accounted for the rest, including the Democratic Senate Campaign Committee, AFSCME, SEIU and others.

On both sides, the candidates and their outside allies are using almost identical themes and messages. Even though independent groups can’t by law coordinate with candidates, nothing prevents them from making use of the same line of attack, the same sound bites, the same video clips. That’s what’s happened in this race. Republicans are attacking Baldwin as an “extreme liberal” – more liberal than Nancy Pelosi and Barack Obama. Democrats are attacking Thompson as an influence peddler, entangled with lobbyists and monied interests, who “changed” when he started making big bucks in the private sector.

Baldwin and her allies are using the same “gotcha” audio and video to go after Thompson on Medicare and taxes. Thompson and his allies are using the same “gotcha” audio and video to go after Baldwin on health care and taxes.

Marquette’s last poll taken Sept. 27-30 sought to capture some of the effects of the Senate air wars on voters. Asked if Baldwin “is one of the most liberal members of Congress and is too liberal for Wisconsin” -- a major theme of GOP ads – 45% of registered voters agreed and 44% disagreed. Asked if Thompson “sold out to special interests and isn’t working for you anymore” -- a major theme of Democratic ads – 49% agreed and 42% disagreed.

But the surest sign of the impact of advertising – and of the partisan hardening among voters that occurs over the course of almost every big campaign -- is the upward arc of each candidate’s “negatives,” the share of voters who view them unfavorably.

In Marquette’s polling, Baldwin’s negatives have gone from 21% in January to 30% in June to 39% in late September. Thompson’s negatives have gone from 31% in January to 36% in June to 48% in late September.

The Wisconsin Voter is a blog about elections, political trends and public opinion in Wisconsin and the Upper Midwest. It is less about politicians than the people who elect them. It’s aimed at political junkies and general readers alike. Its subjects include:

The role this state and region play as electoral battlegrounds.

Voting patterns and trends at the local, state and regional level.

What makes voters here different from voters in other places.

Public opinion and the election climate.

Craig Gilbert is the Journal Sentinel's Washington, D.C. Bureau Chief and national political reporter.

Charting how each of Wisconsin’s 72 counties has trended politically compared to the U.S. as a whole over 60 years of presidential voting. Use the pull down menu to see charts for individual counties. Click here for an explanation of how the charts were done and how to read them.